Comparators are commonly used in integrated circuits (ICs) to compare voltage levels of input signals and produce output signals indicating the result of the comparison. The comparator output typically provides a basis for further switching in the IC.
One particular type of comparator is a window comparator. Window comparators are used for, among other things, the control of voltage regulation circuitry. In a window comparator, an input signal is compared to a high window level and a low window level. When the input signal level exceeds the high level, a first signal is produced. When the input signal level is between the high window level and low window level, a second signal is produced. Finally, when the input signal level is below the low window level, a third signal is produced. Thus, when the input signal is a voltage to be controlled, the signals produced by the window comparator may be used to regulate the voltage of the input signal.
Comparators may be constructed in many different manners. For example, an operational amplifier may be configured to compare two input signals, the operational amplifier producing a first signal when a first input signal level exceeds a second input signal level and a second signal when the second input signal level exceeds the first input signal level. While functioning reliably, the operational amplifiers operate slowly and can consume large amounts of current. Thus, in today's high-speed, low-power circuits, operational amplifier comparator implementations are inadequate.
Other comparator configurations have thus been developed in an attempt to increase speed and reduce power. One particular implementation employed fast stabilizing latches to provide high speed comparisons. The high speed latches, however, were high current consumers. Therefore, differential input sections, were coupled to the high speed latches to reduce the latches current consumption. Even with the differential input sections, however, the configuration still consumed current at levels that exceed the requirements of low power ICs.
Thus, there is a need for a comparator circuit that operates at high speeds and be capable of comparing a plurality of signals so that it may be used in common IC circuitry.